Implantable electrical stimulators may be used to deliver electrical stimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis. In general, an implantable stimulator delivers neurostimulation therapy in the form of electrical pulses. An implantable stimulator may deliver neurostimulation therapy via one or more leads that include electrodes located proximate to target locations associated with the brain, the spinal cord, pelvic nerves, peripheral nerves, or the gastrointestinal tract of a patient. Hence, stimulation may be used in different therapeutic applications, such as deep brain stimulation (DBS), spinal cord stimulation (SCS), pelvic stimulation, gastric stimulation, or peripheral nerve stimulation. Stimulation also may be used for muscle stimulation, e.g., functional electrical stimulation (FES), to promote muscle movement or prevent atrophy.
In general, a clinician selects values for a number of programmable parameters in order to define the electrical stimulation therapy to be delivered by the implantable stimulator to a patient. For example, the clinician ordinarily selects a combination of the electrodes carried by one or more implantable leads, and assigns polarities to the selected electrodes. The selected combination of electrodes and their polarities may collectively be referred to as an electrode configuration. In addition, the clinician selects an amplitude, which may be a current or voltage amplitude, and, in the case of stimulation delivered the patient in the form of electrical pulses, a pulse width and a pulse rate. A group of parameters, such as a group including electrode combination, electrode polarity, amplitude, pulse width and pulse rate, may be referred to as a program in the sense that they drive the neurostimulation therapy to be delivered to the patient. In some applications, an implantable stimulator may deliver stimulation therapy according to multiple programs either simultaneously or on a time-interleaved, overlapping or non-overlapping, basis.
The process of selecting electrode combinations and other stimulation parameters can be time consuming, and may require a great deal of trial and error before a therapeutic program is discovered. The “best” program may be a program that best balances greater clinical efficacy and minimal side effects experienced by the patient. In addition, some programs may consume less power during therapy. The clinician typically needs to test a large number of possible electrode combinations within the electrode set implanted in the patient in order to identify an optimal combination of electrodes and associated polarities. As mentioned previously, an electrode combination is a selected subset of one or more electrodes located on one or more implantable leads coupled to an electrical stimulator. As a portion of the overall parameter selection process, the process of selecting electrodes and the polarities of the electrodes can be particularly time-consuming and tedious.
The clinician may test electrode combinations by manually specifying combinations based on intuition or some idiosyncratic methodology. The clinician may then record notes on the efficacy and side effects of each combination after delivery of stimulation via that combination. In some cases, efficacy and side effects can be observed immediately within the clinic. For example, spinal cord stimulation may produce paresthesia and side effects that can be observed by the clinician based on patient feedback. In other cases, side effects and efficacy may not be apparent until a program has been applied for an extended period of time, as is sometimes the case in deep brain stimulation. Upon receipt of patient feedback and/or observation of symptoms by the clinician, the clinician is able to compare and select from the tested electrode combinations.
In order to improve the efficacy of stimulation therapy, electrical stimulators have grown in capability and complexity. Modern stimulators tend to have larger numbers of possible electrode combinations, larger parameter ranges, and the ability to simultaneously deliver multiple programs by interleaving stimulation pulses according to different programs in time. Although these factors increase the clinician's ability to more finely adjust therapy for a particular patient or disease state, the burden involved in optimizing the device parameters has similarly increased. Unfortunately, fixed reimbursement schedules and scarce clinic time present challenges to effective programming of stimulation therapy.
Existing lead sets include axial leads carrying ring electrodes disposed at different axial positions, and so-called “paddle” leads carrying planar arrays of electrodes. Selection of electrode combinations within an axial lead, a paddle lead, or among two or more different leads presents a challenge to the clinician. The emergence of more complex electrode array geometries presents still further challenges. The design of the user interface used to program the stimulator, in the form of either a physician programmer or patient programmer, has a great impact on the ability to efficiently define and select efficacious stimulation programs.